Former U.S. Senate candidate Larry Rhoden endorsed his victorious rival Mike Rounds on Friday at the South Dakota Republican Party’s convention.

Rhoden, who refrained from attacking Rounds in the final months of the campaign, was expected to back Rounds eventually. But his appearance Friday was a surprise.

“Surprise!” Rhoden said, after Sen. John Thune introduced him. “I see a couple of people in the back saying, ‘I thought he lost the primary.’ ”

Rhoden, a state senator, said Republicans need to be unified.

“We need to regain focus now on the vast majority of issues and principles that don’t divide us, but bring us together,” Rhoden said.

Rounds thanked Rhoden and former candidate Jason Ravnsborg for their support. He made no mention of Stace Nelson, who is supporting independent candidate Gordon Howie in the general Senate election, nor of Annette Bosworth, who is facing 12 charges of alleged election law violations.

Party unity was a theme at the Republican convention, just as it was in 2012. In both years, party leaders sought to downplay tensions between them and conservative activists in the wake of divisive primaries.

Both Rounds and party chairman Craig Lawrence cited a quote attributed to Ronald Reagan: “The person who agrees with you 80 percent of the time is a friend and an ally — not a 20 percent traitor.”

“We will disagree at times, but we must not be lured into disunity,” Lawrence said in his opening speech.

Rounds’ own speech to the convention was an appeal to “take back our country” by giving Republicans control of the U.S. Senate. The former governor focused his attacks on President Obama, Senate Majority leader Harry Reid, and federal “bureaucrats.”

He also discussed his decision to run for the U.S. Senate. He said he was urged to run for the Senate in 2008, while still governor, by then-President George W. Bush. That would have set up a matchup between Rounds and Sen. Tim Johnson. Rounds declined at the time.

In 2011, Thune, and Sens. Mike Johanns of Nebraska and John Hoeven of North Dakota encouraged Rounds to run. Rounds said he was resistant to those calls until Thune brought him to Washington, D.C., to meet the Senate GOP caucus.